My swamp cooler / box fan . . . review
Tockk
http://www.electric-fan.com/product/BFC2200.aspx
for about 1/3 off, and it's been rainy and humid here in the Dallas area for
the past while. Haven't had the chance to use it until yesterday, when it
was hot and 33% humidity (according to the TV weatherman).
I fired it up, and used a thermometer to read the temperature of air going
in vs. air coming out. In my apartment, it read 95 degrees going in to the
fan, and 84 coming out of the fan. Not bad.
As far as ability to cool a room, well, it's limited. I have two windows
seperated by about 6 feet of wall space. I put the cooler-fan in front of
one window, and I have another fan in the other window that pushes the air
to the outside. It's pretty good if you get right in front of the airflow,
but anywhere else in the room, you won't feel much relief. It's also
somewhat noisy; it took a little getting used to on the slow speed. I doubt
most people would want to deal with the high speed--too noisy.
At night, it dropped the temperture 10 degrees F, from 90 F to 80 F.
All in all, it's ok . . . I've gotten used to sleeping in 80 degree heat (no
covers), and it provided sufficient relief to give a restful night sleep.
What's nice is the $$$ I saved from not running the AC. Using this thing
for 30 days will save me around $2 a night, or $60 a month. It'll pay for
itself in less than 2 months, and it'll be gravy after that.
It holds a few gallons of water, which isn't enough for an 8 hour run.
I'll probably add a 5 gallon water bottle held upside down, with a feeder
tube so that it fills up the fan's resovoir when it runs low. That ought
to fix that problem . . .
If it starts to rain again like it had been up through July, I'll just use
the fan by itself, and that should be ok.
--Just some notes on this thing . . . FYI . . .
m...@privacy.net
>I bought one of these a while ago:
>http://www.electric-fan.com/product/BFC2200.aspx
Interesting
Had no idea they even made such a thing!
But isn't Dallas a less than optimal place for it?
m...@privacy.net
>I bought one of these a while ago:
>http://www.electric-fan.com/product/BFC2200.aspx
>for about 1/3 off, and it's been rainy and humid here in the Dallas area for
>the past while. Haven't had the chance to use it until yesterday, when it
>was hot and 33% humidity (according to the TV weatherman).
On thing I'm having hard time finding is a portable
fan that doesn't suck up dust form the floor and spew
it everywhere
Seems as most portable fans are made to set on the
floor. To my thinking sucking air form that area is NOT
a good idea...if you have allergies sand such
skar...@gmail.com
> As far as ability to cool a room, well, it's limited. I have two windows
> seperated by about 6 feet of wall space. I put the cooler-fan in front of
Two windows on the same wall and 6' apart? That is not a good
configuration (on a fluid dynamics perspective). Cooled air is being
flushed out immediately by the exhaust fan.
Keep all the doors and windows closed and use the cooler in the room
just like a fan. If you insist on fresh (outside) air, do one of the
following.
1) Keep the exhaust fan in a window as far away as possible from the
inlet window.
2) If the above is not possible, just remove the exhaust fan and close
the outlet window and you will be much better off.
3) Last choice, take out the exhaust fan from the window, keep the
window shutter open just 2 or 3 inches.
There is really no need to drive out the air - it finds its way out
all by itself.
Melinda Meahan - take out TRASH to reply
> I bought one of these a while ago:
> http://www.electric-fan.com/product/BFC2200.aspx
> for about 1/3 off, and it's been rainy and humid here in the Dallas area for
> the past while. Haven't had the chance to use it until yesterday, when it
> was hot and 33% humidity (according to the TV weatherman).
A swamp cooler does not work anywhere near as well in a humid
environment than in a dry one, but apart from that, we have one here in
northern California and it keeps the house nicely cool and hardly uses
any more electricity than when we had fans running all over the house.
--
Every job is a self-portrait of the person who does it. Autograph your
work with excellence.
Tockk
<m...@privacy.net> wrote
> But isn't Dallas a less than optimal place for it?
For the most part, yes. The lower the humidity, the better it works.
Yesterday, the humidity was 33%, sounded fairly low, so I figured I'd give
it a try. Worked ok.
I dunno how often the humidity gets that low in Dallas. It's been very
humid (it's rained much more than ususal), but it's finally dried out a bit,
and I think it'll work ok for the next week or so.
Jerry
As a data point, the general rule of thumb here in Phoenix is coolers
are effective up to a dew point of 50 to 55 degrees.
nicks...@ece.villanova.edu
>I bought one of these a while ago:
http://www.electric-fan.com/product/BFC2200.aspx
>for about 1/3 off, and it's been rainy and humid here in the Dallas area for
>the past while. Haven't had the chance to use it until yesterday, when it
>was hot and 33% humidity (according to the TV weatherman).
The ASHRAE 55-2004 comfort standard says that's very hot, with a predicted
mean vote of 3.07 on a scale of -3 (very cold) to 0 (perfectly comfortable)
to +3 (very hot.)
T (C) RH% Clo PMV PPD%
35 33 .5 3.07171 99.38564
The standard predicts that 99.38564% of people surveyed would be dissatisfied.
>I fired it up, and used a thermometer to read the temperature of air going
>in vs. air coming out. In my apartment, it read 95 degrees going in to the
>fan, and 84 coming out of the fan.
The web site says it moves 415 cfm, and 1 Btu/h can cool 1 cfm about 1 F
and 1000 Btu can evaporate 1 pound of water, so you were cooling the air by
about 415(95-84) = 4565 Btu/h with about 4.565 pounds per hour of water.
With an outdoor vapor pressure Po = 0.33e^(17.863-9621/(460+95)) = 0.559 "Hg
(using a Clausius-Clapeyron approximation--ask Caryn), and humidity ratio
wo = 0.62198/(29.921/Po-1) = 0.00185 pounds of water per pound of dry air
(1 ft^3 of 70 F air weighs 0.075 pounds), 4.565 = 60x415x0.075(wi-wo) makes
wi = 0.014295 and Pi = 0.6877 "Hg with a 57.6% RH indoors, which would be
a lot more comfy:
T (C) RH% Clo PMV PPD%
28.88889 57.6 .5 .8197596 19.1735
Only 19.1735% of the people would be dissatisfied.
If you could evaporate 6 vs 4.565 pounds of water per hour, you could lower
the outdoor air temp to 80.5 F with wi = 0.01506 and a 66.3% RH, which would
be even more comfy:
T (C) RH% Clo PMV PPD%
26.94445 66.3 .5 6.351899E02 5.083534
The ASHRAE comfort zone is defined by -0.5 < PMV < 0.5. They also limit
the humidity ratio to 0.0120 max, so wi = 0.014295 is outside the zone,
even though the calc below suggests it would be close to perfectly
comfortable, with 5.083534 Per cent of People Dissatisfied.
(You can't please everyone with one condition.)
>As far as ability to cool a room, well, it's limited.
You may be cooling more outdoor air than you need.
>I have two windows seperated by about 6 feet of wall space. I put
>the cooler-fan in front of one window, and I have another fan
>in the other window that pushes the air to the outside.
You might enjoy moving the cooler into the room and only running it when
the room temp rises to 80.5 F with a thermostat, and only running the fan
when the room RH rises to 66.3%, with a humidistat, eg this one:
http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611632220
>It holds a few gallons of water, which isn't enough for an 8 hour run.
If you are only cooling the room and C cfm of outdoor air with P pounds
of water per hour, and the room thermal conductance is (say) 50 Btu/h-F,
1000P = (95-80.5)(50+C) and P = 60C0.075(wi-wo) make P = 1.73 lb/h and
C = 120 cfm, so the 3.25 gallon reservoir would last 3.25x8.33/1.73 =
15.6 hours.
50 CLO =.5'clothing insulation (clo)
60 MET=1.1'metabolic rate (met)
70 WME=0'external work (met)
80 TA=(80.5-32)/1.8'air temp (C)
90 TR=TA'mean radiant temp (C)
100 VEL=.5'air velocity
120 RH=66.3'relative humidity (%)
130 PA=0'water vapor pressure
140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
160 ICL=.155*CLO'clothing resistance (m^2K/W)
170 M=MET*58.15'metabolic rate (W/m^2)
180 W=WME*58.15'external work in (W/m^2)
190 MW=M-W'internal heat production
200 IF ICL<.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
210 HCF=12.1*SQR(VEL)'forced convection conductance
220 TAA=TA+273'air temp (K)
230 TRA=TR+273'mean radiant temp (K)
250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
260 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermediate values
300 P5=308.7-.028*MW+P2*(TRA/100)^4
310 XN=TCLA/100
320 XF=XN
330 N=0'number of iterations
340 EPS=.00015'stop iteration when met
350 XF=(XF+XN)/2'natural convection conductance
360 HCN=2.38*ABS(100*XF-TAA)^.25
370 IF HCF>HCN THEN HC=HCF ELSE HC=HCN
380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
390 N=N+1
400 IF N>150 GOTO 550
410 IF ABS(XN-XF)>EPS GOTO 350
420 TCL=100*XN-273'clothing surface temp (C)
440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
450 IF MW>58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
460 HL3=.000017*M*(5867-PA)'latent respiration heat loss
470 HL4=.0014*M*(34-TA)'dry respiration heat loss
480 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
490 HL6=FCL*HC*(TCL-TA)'heat loss by convection
510 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
520 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
530 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
540 GOTO 580
550 PMV=99999!:PPD=100
580 PRINT TA,RH,CLO,PMV,PPD
T (C) RH% Clo PMV PPD%
35 33 .5 3.07171 99.38564
28.88889 57.6 .5 .8197596 19.1735
26.94445 66.3 .5 6.351899E02 5.083534
Nick
Tockk
Thanks,
--Tock
Abby Normal
Am I reading you correct that you are finally using outside air?
Abby Normal
Nick has been learning evaporative cooling for a couple years online
now, he may understand it one day yet :-)
Abby Normal
>
> - Show quoted text -
Nope was the original poster using the outside air. Nick still cannot
grasp the inherent flaw with using evaporative cooling on return air.
.p.jm@see_my_sig_for_address.com
Give him another couple of decades, maybe he'll catch on.
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Bet he doesnt. He backs himself into these logical corners and
is so thick that he never ever does manage to work out the problem.